We have recently completed a study at the GCRC where we found a striking abnormality of the diurnal rhythm of plasma melatonin in non-alcoholic cirrhotic subjects. This consisted of a delayed onset of melatonin secretion as well as a delay in the peak time of nocturnal melatonin levels--findings that are suggestive of a phase shift of the "biological clock." Correction of the parameters suggestive of a disruption of the circadian clock would confirm the hypothesized relation between hepatic encephalopathy and circadian function.